Cleft fastener for uniting materials and method of forming the same



Jan. 27, 1953 I. A. WILLIAMS "2,626,637

CLEFT FASTENER FOR UNITING MATERIALS AND METHOD OF FORMING THE SAME Filed May 25. 1949 2 SHEETS-SHEET 1 iii [NIH

INKENTQR. Ivan ALWz IZ lams I. A. WILLIAMS CLEFT FASTENER FOR UNITING MATERI Jan. 27, 1953 ALS AND METHOD QF FORMING THE SAME 2 SHEETSSHEET 2 Filed May 25, 1949 s .m q mm WU my mW V 4 mm a A N R w M mm. I .YMW h \E 7 M- w mum I l u om d 1/ QNM Om,\ F \rr L i m v r v s 2 5% \W m E 37 i Patented Jan. 27, 1953 FT'ENT] OFg FIgICE;

opera: FASTENEBFQB UNITING MATERIALS a nun vregrnonor; romaine 'rrns se ne Ivan A. Wiiliams, fertiand Oregh A m g gug 23 1949, Serial No. 94,732 v 10 C1aims. (Ci. 189-36-).

heg re ent.inventi r ies r9a w 1S P r-t eeter a 5; together "superwh g-l r V as amine we practice en d-to a'novelidie for-use inconjunction aforesaid E?QH?1 E- Many methods heretofore have been practiced of aterial particularly metal terial, $6 a nor elf channeled .i i m iue vi rla m h A and fastening them together I by means bolts, crews, rivets, spot welds and e are atta ned; is e s l a 1.. my v ene!- ia es t e te 2,-25 8,- issued September 2; 1941; for Fastening ie nentiahfdl ei he F f las sam d, in-mi/Y mreasrai s i r P te 3 Q i une) 3 zrfei i s ih-z d A aep r e. m thpeeisele ee an im n h above patents 1 181561; forth in my copending apq hfi 'e .o, Uniting Punch and Die;

Iniacc'ordanee Withythe method disclosed in theforegoing. patents and patentapplication super-f imposedpieces of {material are placed between a punch and die inia press assemblv; "The' punch' and die then are moved towardeach otherso that their cutting edges coact to form =spacedi inci sions entirely through the material. Next the seams of material between the incisions are deinthefdi'rection of-the die until substantial 'portio ns lie -beyond the plane of that surface adjacent the die This deformation is accomw panix llby teending and-stretching of portions of t r atfihs f d' n t we he a e inc ons, pattern conforming to the shape of the punch; The dent n sections of the deiorm edportionsthen are subjected to pressure against.

pres'efnt invention is directeda aet neeliebi z h r e tplication-tqr United States Letters Patent, --Serial- 749,317 fil ed -Maylj l'94'7-y for Material venfion t m deas eili e and? e re dn ingthe material displaced during the forrnation' of my stitch substantiallyviithout the material adjacent the points Where it k'ey s "to gether the overlying pieces of material; This forms a relatively strong-fastener..-

It is another object'of the present invention to provide a method and 'die for uh-iting'cvrl'ying...

pieces of material whereby-it possible to: direct the distribution of material formingthe fasteningelements in a predetermined :dir ection thus avoiding setting up stresses andstrains m the body of the material ur'iited whicl may cause thefl warping or disto'rtionfof the same.

Still another'object of the presentinvention is the provisionof a method for uniting overlying; l

pieces of material whichrequfies a minimumho'f pressure to operate, thus making the applica:

tion of the method readily applicable toistee'l and other hard structural materials.

It is still another object ofitheipresentuinvenetion to provide a-mthod anddieiforthe. fasten, ing together of overtying pieces ofvrriaterialvvhich, are rapid, economical-' ton-useg andlwhichiresultt in the formation of aistrong.lstitchmwidely .apfi.

plicable tot he' joining together 10f :materialscin a variety of situations.

The manner in whichithe foregoing: and other. objects of the invention ar'eaccomplishedwillrbee apparent from the following specificationuand, claims considered 7 together with \the. drawings wherein like parts arehindicatedt'by like numerals and wherein:

Figure 1 is a. composite, side 4 .view of a punch;

and die positioned inthetthroatgoffia press and;

operating on. superimposed pieces of materia1- to form the herein described fastening element? Figure 2 is anendviewof thediepfeFigllreel;

Figure 3 is an edgeriem partly incsection-pr; the punch and die .of Figure 1 inthe initial stages of formingcby the method oth'the present ,inye

tion a fastening-element or;stitchegtending g througheover y p cesof mate.

Figure 4 is ,a view similarstdnth t :of Figurej illustrating advanced positionsaofmunchzand 1die and showingthe final,stages;of the'irormation not;

the fastening'element;

Figure 5 is a longitudinal. view,inesectionrofsaa stitch formed by theitoperationof th'epunch and. die of Figure 1;

Figure 6 is a transverse. view-in SGQtiOI'l-aOfJthB stitch of Figure,5; l l

Figure 7 is a. side .view in.e1evation-.:i11ustrating.- the construction and .applieatiomof fafdie er ffnodiif fied construction;

Figure 8 is an end view of the die of Figure 7;

Figure 9 is a view similar to that of Figure 4, but illustrating the die of Figure 7 cooperating with a punch in forming a fastening element through overlying pieces of material; and

Figures 10 and 11 are sectional views in elevation illustrating another embodiment of the method of forming a fastening element through overlying pieces of material in accordance with the present invention.

Generally stated, the hereindescribed method of uniting overlying pieces of material comprises displacing a portion of one of the overlying pieces through another of the same, and then penetrating the displaced portion centrally in a direction which is either the same as the direction of displacement, or opposite thereto. This spreads the displaced portion of one of the pieces at right angles to the direction of displacement so that it underlies and engages (Figures 6 and 11) another of the pieces, thereby efiectively locking the pieces together and forming a fastener having a channel or indentation in its central portion.

The fastening element thus may be formed by means of a punch having cutting edges at one of its ends and cooperating with a die provided with cutters, the edges of which are placed to correspond with the cutting edges of the punch. On the anvil portion of the die is a projection adapted to pentrate and spread the material between the incisions formed by the cutting edges of the punch and die and displaced in the direction of the anvil. The spread material thus is forced into wedging engagement with and forced to underlie portions of the superimposed pieces of material, thereby locking them together.

It will be apparent that, since the penetration of the displaced material occurs centrally, the edge portions which are displaced outwardly to underlie the pieces to be joined will retain substantially their. original thicknesses and thus make a strong stitch. Furthermore, by providing an elongated projection on the anvil, the spreading of the displaced material may be directed so that it spreads laterally almost exclusively. This minimizes the setting up of stresses and strains within the body of the material which may cause it to warp and wind. Also, since the fastener is formed by penetration and spreading rather than by upsetting, the pressure requirements for its formation are relatively low so that it is readily applicable to the fastening together of sheets of steel and analogous materials.

One embodiment of the punch and die of the present invention is shown in Figures 1 to 4, inclusive. In those figures, overlying portions of metal sheets or other pieces of material to be united are represented generally by the numerals Ill and II. These are shown as they are arranged in position in the throat of a suitable press mechanism comprising the punch l2 and the die I3. The punch may be of various sizes and shapes but in the embodiment illustrated comprises a body section l2a and a cutting section 121). The cutting section advantageously may be semi-hexagonal in shape, as viewed from the side (Fig. 1), so as to present three normally planar surfaces to the material operated upon. The center surface I which comes in contact with the material is sufficiently long to produce a stitch of the desired length and sufliciently wide to correspond to the distance between the 4 cutting edges of the die with which it cooperates to form spaced incisions through the material, this being the first of the sequence of operations producing the final fastening element or stitch.

The edge surfaces 12d and We of the punch initially are positioned opposite the open ends of the die. They act primarily as forming members for bending or deforming and stretching the material between the spaced incisions produced by the coaction of the punch and die. Since the bending occurs over a substantial area when using a punch of the form illustrated, there is avoided localized stretching and thinning of the material and consequent weakening of the stitch.

The die I3 comprises a body portion l3a, a transversely apertured anvil portion I32) and a plurality of transversely perforated cutting elements or cutters It. The body portion of the die may assume various forms to meet the needs of various types of operations and may have one or a plurality of anvils attached thereto. In the usual application, it may comprise an elongated member preferably circular in cross section and having an integrally formed terminal portion reduced in size to form an anvil having a surface directly opposing the punch.

The surface of the anvil is provided with a tapered projection I301. This terminates in a point which, although sufficiently sharp to penetrate the material being operated upon, has a slight radius to avoid dulling and nicking of its edge during use. The projection preferably is elongated in a direction parallel to the cutting edges of the cutter. Its upper limit is on a plane just below the plane of the cutter edges as they engage the materials being united. Its width is sufficient to give the desired degree of spreading.

Hence as the punch descends toward the anvil and shears through the overlying pieces of material, the displaced portion between the inci sions is driven against the projection on the anvil and is penetrated thereby, thus accomplishing a lateral spreading sufficient to engage the underlying, piece of material, the two split sections working their way downwardly between the anvil and the inner faces of the cutters and separating the cutters slightly near the end of the stroke (Figure 4).

The anvil portion of the die has opposed. side faces against which the cutting members are placed, and is transversely apertured to provide an opening I5 which is in substantial registration with perforations i6 (clearance holes) in the cuttingmembers. As will appear more fully hereinafter, this provides a construction for attaching the cutters to the die rotatably in the planes of their cutting edges and yieldably laterally with respect to the anvil.

The anvil portion preferably is Wider at its base than at its top, thereby imparting converg ence to the planar side faces adjacent the cutters as well as to the cutters themselves. Although the degree of convergence may be varied, it preferably is about 6 from the longitudinal axis of the anvil; Such a construction is preferred because it provides an anvil surface which is relatively wide as compared with the distance be tween the cutting edges of the cutter and the Width of the punch, while retaining a desired ree of parallelism between the opposed edges of the cutters and the projection lSd (Figure 2).

When operating on non-scaling materials, the opposed side faces of the anvil may contact substantially the entire side surface area of the cutse. Hpweverjg w eathee ieris t -bau ed upon. coated metals such I as lgalvanizediron; or upY mater-ials having particlesof;scale on theirs L faces it; is desirable -to provide means .for ac commodatinga and. disposing.- of the particles of, refuse material which otherwise. might collect upon and interfere with the action of thedie Such-meansmay comprise, cavities interposed between the; anviland the cutters,- for example as concavities inlthe latte or as recesses in the formers Preferably, there are provided recesses l7. -in;-theanvil, extending; across .theside faces thereof T and. communifiatingv with V the transverse, aperture therein, These recesses accomel. moda-teeparticles ofscale, --coating .m-atrial, and r the lil;e formed: during operation of the .die and.

. prevent, suchparticles-from disturbing thaposi;

tiomof-the outters-andthe .close fit .betweenthe. cutting edges, ofthe punch: and die.

oul rs 18 are or d d n t es o y Po tion. of; ,the dies adjacent the opposite f side; "faces, of he-r m hese spreferablv c nform- .to. v e. shapeof the ;-edge surface, of the, cutters. and; serve supporting surfacestherefor so that the crushing and-:displacing;;stresses s developed ,dur ing op erationfof, the the are resisted by the body thereof; As a result; the weaker'members of the die assembly, particularly the ,shaft or other means --employed for; mountingthe cutters,. are protected from damage.

Provision ,also is made for protecting the cutting edges of thedie. .Locatedin onnext toeach of I the shoulders are recesses or cavities; l9.- These may comprisegrooves running alonglthe. base of each of the'opposed side faces of the anvil so that they-;underlie,- the cutting edges of the cutting .elements; When the ,latter: are forced against the shoulders-during operation of the press, the cutting edges then-,will lie Within the grooves, which serve asrreliefs .andpreventthe striking of the cutting edges against the body of the die.;

The cutters i l may comprise substantially circular, disc shaped elements having centrally-locatedtransverse apertures. Their edges prefera bly are beveled so that during operation of thedie they form recesses or indentations 7 29 (Fig. 6) lying immediately outside the spaced incisions and in the surface of the piece II Which is .ad-,

jacent'the die assembly l3. The degreeof, bevel axes} the samebeing perpendicular to the planes,

of the cutters... Also, they are mounted yieldably. laterally. with respect .to the anvil, Preferred, means forsecuring such rotatable and yieldable attachment comprises a shaft or pin, 2! extend-,. ing through .the transverse aperture J5 ,in the, anvil and also through the. apertures IS in the cutting elements. The cross-sectional, dimension; of the shaft in comparison to the size of theaper tures whichit, penetrates .isysuch thatit fits snugly Within, the aperture through theanyil but loosely within, the-aperturesv in the putting me ts. This -s.,- esirab S n a l s t. hestweenv the pin and the anvil gives mcreased stren th toathe. assembl the .r o y ,0f. the;pin,act-... ing: 1to. suppcrtthe topportion of the anvil; which; 1

and the cutters is desired I 1150; enable .,the' .cutterstoslip up and down to :a limited extentpver the side-.faces of the anvil. As a result, they do not exert a 'shearingaction upon thev shaft on which they; are mounted, but ratherare displaceddownWardl-y sufficiently sothat they bear against the, shou1ders -on thebody portion-wof the die which-thus resists the forcepf-thepunching.operation. The resilient means requiredto mount the ,outters yielclably laterally with respect to the anvil may be provided by springs attachedin -a suitable manner to the endsof the shaf-t and bearing against the outside surface of the cuting a nut and screwthereon, or by other suitable means. It should be noted thatthetensionofthe springv should be justsuflicient to hold the cutters normallyin closecontact with the side faces. of-thaanvil and to return thempromptlyto ;-this. position-aftertheir lateral displacement during operation of the diet; If the springtension is -too weak, this: .desired action, is not obtained. Ognithe other hand, if it is'too. strong,-the I springs will opposethe lateral displacement of the cutterstoo strongly and thus interfere with or prevent proper functioning of the die.

Inloperation, the punch and die; members are mounted in a press mechanism" with the punch positioned either above or belowthe die, or with the two members disposedhorizontally ,or obliquely with respect to each-other. Either punch or die,;or both, may be the movable parts of the assembly. These factors-arevariable to meet the requirements of the stitchingoperation. It

is preferred in the usual application however,

to-have yth die as the lower stationary-member andthe punch as the upper; movable memberso that upon actuation it descends toward the anvil.

Furthermore, a single punch and die may be used-toproduce a single fastening element or stitch in anygiven 0peration, or a. pluralityof punchesor oliesmay beQmounted on common membersin the press so as to produce a cor-. respondingwnumber of fastening elements inv a single operation, I

Upon moving the punch and die toward each other; their cutting edges coact -tdforrn spaced incisions through overlying portions of the "mterial operated upon. Inaddition, pressure ex-- rted r-t e beve l d p ns ed e f E h le 4 dent s; urae-.- hej mat ial? 'm e esses rmti i m ed atel u side- 0f the spaced incisions. Deformation of thematerial between the incisions in 'the direc: tiOI ,;;Of the anvilof :the die also occurs to. such an extent, that it is displaced beyond the plane w of the inner surfaces or ceilings ofthe indentations, During this deformation, portions -of the material; are-bent and stretched-toward the die in; pattern conforming tothe central surface nds the o in l: de urfa es of the pu ch.-

- Hence thereeare ,formecl; displaced portions; of I he materi lin the orts pfz sst s bai s defi ed b .e. pa ed nc o e nd: t xt ndina tir y beyond-that surfacepf, the overlying .materials whic ad a e t h e-:-

As the punch displacessegments-of the overly;

ing materials in the direction of the anvil, the projection on the latter enters the lower surface of the displaced material, penetrating it and spreading it laterally until it underlies the undisplaced material in such a manner as to prevent retraction of the deformed material through the space between the incisions. This forms the fastening element or stitch. It will be noted that the degree of penetration of the projection on the anvil into the displaced material need only be sufiicient to enter the overlying segment of the same, spreading it sufficiently to engage the under surface of the lower piece. It will further be noted (Figures 4 and 6) that as the projection on the anvil penetrates the lower layer of deformed material and enters the upper layer of the same, the central portion of the former may be stretched so that a film conforming generally to the shape of the projection may be projected into the upper layer. However, there is no thinning of the edge portions of the deformed material which are spread to underlie the undeformed material and as a result the fastener is correspondingly strong.

The splitting and lateral spreading of displaced material obviously causes the exertion of pressure against the inner faces of the cutting elements of the die. These are yieldably mounted, however, and spread to accommodate the lateral flow of the expanded material and to permit retraction of the die from the finished fastener.

Another effect occurring during operation of the assembly is the axial displacement of the cutting elements with respect to the anvil so that their lower surfaces rest upon the shoulder portions of the body of the die. The operating stresses developed in the punch and die thus are transmitted to the stronger section of the die assembly.

A further action is the successive presentation of fresh cutting edges of the cutter elements to the material operated upon. Since the cutters are mounted rotatably on the die, they may be rotated manually or by the lateral removal of the stitched material from the press. There thus is made available a multiplicity of cutting edges which may be presented successively to the surface of the material operated upon. This obviously greatly prolongs the life of the die. The retention of a sharp cutting edge also is made possible by reason of the fact that, although the edge portions of the cutting elements are displaced downwardly against the shoulders of the body portion of the die during operation of the press, the cutting dges are protected during this action by the fact of their being stationed above recesses or reliefs.

Still a further action taking place is the elimination of pieces of scale and other fragmentary material from the space between the side faces of the anvil and the cutters. As is indicated above, such fragmentary material derives from the disintegration of the materials processed, the peeling oif of coating materials, as in the case of galvanized iron, or the loosening of scale or other substance which may be present on the surface of the material. This matter collects principally in the recesses provided on either side of the anvil by having the side faces of the anvil recessed, for example, or by employing cutting elements the inner faces of which are concave in shape. It automatically is eliminated from the die by the jarring and air currents produced by the vigorous snap with which the cutters return to their normal positions when the die is removed from the stitch, and by the rotation of the cutters caused by the lateral removal of the work from the press. In this manner, there is prevented the accumulation of residual and foreign material which would crowd the cutting elements outwardly to a position in which the cutting edges would not register with the cutting edges of the punch.

Another embodiment of the die of the present invention is illustrated in Figures '7 to 9. The punch which cooperates with the die in uniting superimposed pieces of material 30, 3| has a construction similar to that illustrated in connection with the embodiment of Figures 1 to 4. Thus the punch 32 comprises a body section 32a and a cutting section 321), the latter being semi-hexagonal in shape as viewed from the side so as to present three normally planar surfaces to the material operated upon. The center surface, 320, which comes in contact with the material is sufl'iciently long to produce a stitch of the desired length and suificiently wide to correspond to the distance between the cutting edges of the die with which it cooperates to form spaced incisions through the material. Also present on the punch are the edge surfaces 32d which initially are positioned opposite the open ends of the die and therefore act primarily as forming members for bending or deforming and stretching the material between the spaced incisions produced by the coaction of the punch and die.

The die 33 comprises a body portion 33a, a transversely apertured anvil portion 33b, and a plurality of transversely perforated cutting elements or cutters 34. The body portion of the die preferably comprises an elongated member circular in cross section and having an integrally formed terminal portion reduced in size to form an anvil directly opposing the punch.

On the surface of the anvil is a projection 33d, which is analogous in position, size, and function to the projection 13d of the embodiment of Figures 1 to 4. Thus it may be a tapered member terminating in a slightly rounded point and extending upwardly to a plane just below the plane of the cutting edges of the cutter, It preferably is elongated so that it exerts a cleaving action as well as a penetrating action on the displaced material, the direction of elongation being substantially parallel to the cutting edges of the cutters.

The anvil portion of the die has opposed side faces against which the cutting members are placed and is transversely apertured to provide an opening 35 which is in substantial registr tion with perforations in the cutting members. It preferably is wider at its base than at its top, thereby imparting convergence to the anvil side faces as Well as to the cutters which are placed thereagainst.

As in the previously described embodiment, it is preferred to provide recesses 31 in the side faces communicating with the transverse aperture 35 therein, these serving the function of accommodating refuse particles formed during the stitching operation. It also is preferred to provide shoulders 38 in the body portion of the die against which the cutters bear, thereby resisting the thrust of the punching operation with the body of the die.

In this embodiment, the cutters 34 comprise substantially rectangular flat plates made of steel or similar material and having the two edges opposite the punch substantially parallel with each other. When in place against the opposite sides of the anvil, they converge slightly toward the end thereof, abut against the shoulders 38 onthe bodyportion' and overlie the recesses 31 communicating withthetransverse aperture 35 through the die.

The desired resiliency to impart lateral. yieldability to the cutters is provided by the springs 4|. Such a springis disposed adjacent the outer side surface of at least one of the cutters and is adapted to bear against the same to hold it yieldably against the, anvil-side face.

When the cutters and spring elements. are placed adjacent the anvil with theperforations in all of these members in substantial alignment, the opportunity is affordedfor the introduction of means for connecting themand thus attachns the cutterst t e die-a Su h means. pre ably comprise. the shaft or pin; 42 extending through all of the apertures and riveted, spun, screwed, or otherwise, manipulatedto secure the cutters to the anvil under tension-of the spring. It will be apparent that when the transverse aperture through the anvil is, sufficiently large to permit the pin 42 to slide therein, the spring member need be appliedtothe outer face of one cutter only, since when the cutters are spread, thespring action will-be transmittedthro lgh the pin to the cutter not furnished with a spring. This effect is explained fully in my copending application referred to above, Serial gNumber The operation of the die of Figures 7 to 9 is similar to that of the die of Figures 1 to 4, described, above, with the exceptionthat it does not operate to provide substantial recesses in the lower surface of the underlyingpieceof material, nor do the cutters rotate to present fresh cutting edges to the work. Upon moving the punch and die toward each other, the first effect is the coaction of the cutting edges of the punch and die to form spaced incisions through the material.

contemporaneously with. the formation ofv these incisions, the material therebetween is displaced in the direction of the anvil and brought in contact with the projection 32d. The latter penetrates and spreads the underlying displaced segment and at least part of the overlying segment. As the material is spread laterally to follow the contours of the projection, it wedges against the lower surface of the undisplaoed material, thereby spanning the space between the incisions and forming laterally extending keys which prevent retraction of the displaced material and fastens the pieces together.

Hence I have provided a method, and a fastener, together with a die for their practice and formation, by means of which I am able to unite superimposed pieces of material rapidly and securely. Maximum strength is afiorded to the fastening elements by reason of the fact that there is no thinning of the displaced material at the points of contact with the und'isplaced material. Furthermore, the direction of spreading of the displaced material to form the keys may be directed laterally. As a result, the tendency to stretch the body of the material longitudinally during formation of the stitches is eliminated. This minimizes the tendency of the stitched material to twist, wind, Or warp. Because of the ease with which the projection on the anvil penetrates the displaced material and spreads it laterally to form the stitch, the pressure requirements of the punch and die mechanism are relatively low. Hence the method of the invention may be practiced upon materials such as steel sheets of substantial thickness.

It will be apparent to one skilled in the art that,

althoughI .have described andillustrated the present invention. with reference to overlying pieces of-material in-asubstantially horizontal position, the one .piece. being abovethe other piece,.-. the.inventionv is equally applicable to the situations inowhich the pieceslmaybe vertical, orHat-any. anglewith. respect to the vertical. Furthermore, although reference has been made to the construction in which .thepunch is the movable -member, the .die .remaining stationary, the inventionalsoiis. applicable where the die is the movable member orwhere both punch and die are advanced toward eachother.

Still further, althoughzthe invention has been describedv in terms ..of .a simultaneous incising and penetrating action, these operations may be effected stepwise, the ...incising and deformation of thematerialbetween the incisions being carried outin separateoperations, followed by the penetration and spreading of the. incised and de formed material to formlaterally extending keys. In the latter case, thedirection of the penetration mayobviously be eitherin .thedirection of the deformation or opposite thereto. If it is in the direction .of the deformation, as illustrated in Figures 10 and. 11,. the degree of penetration of. the penetrating member d8 cooperating with theanvi] 49 :needbe-relatively slight, beingonly sufiicient tospread thedeformed portion of the upper layer-of. material 50-until it underlies the outer surface of thelower-layer of material 5! on eitherside of thespaced incisions. This imparts maximum strength to the fastener, with spreading of .a minimum amount of deformed materia Having now described my invention in preferredembodiments, I claim as newand desir to protect by Letters Patent.

l. The method of-uniting overlying pieces of material which comprises forming -a;pair of substantially parallel spaced incisions through both of the-pieces, bending-the material betweenthe incisions outwardlyuntil the displaced portion of one of the pieces lies only a minimum clearance distance beyond the outer surf-ace of the other of the pieces, and penetrating the said displaced portion centrally, thereby spreading it laterally until it underlies and engages the said outer surface of the other of the pieces, the spread material retaining substantially its original thickness, thereby locking the pieces together through an integral fastener.

2. The method of claim 1 wherein the direc-- tion of penetration of the displaced portion of said one of the pieces is from the direction of the outer surface of the same.

3. The method of claim 1 wherein the direction of penetration of the displaced portion of said one of the pieces is from the direction of the outer surface of said other of the pieces.

4. The method of uniting overlying pieces of material which comprises forming a pair of substantially parallel spaced incisions through both of the pieces, bending the material between the incisions outwardly until the displaced portion of one of the pieces lies only a minimum clearance distance beyond the outer surface of the other of the pieces, and laterally spreading said displaced portion without substantial thinning of its outer margins by cleaving it centrally, the direction of cleavage being substantially parallel to that of the incisions, thereby causing it to underlie and engage the other of the pieces, to lock the pieces together through an integral fastener of substantial strength,

5. The method of uniting overlying pieces of material which comprises forming a pair of substantially parallel spaced incisions through both of the pieces, forming a pair of recesses one outside of each incision and communicating therewith, bending the material between the incisions outwardly until the displaced portion of one of the pieces lies only a minimum clearance distance beyond the outer surfaces of the recessed portions of the other of the pieces, and spreading the displaced portion laterally into said recesses Without substantial thinning of its outer margins by penetrating it centrally, thereby causing it to underlie and engage the other of the pieces, to lock the pieces together through an integral fastener of substantial strength.

6. The method of claim 5 wherein the direction of penetration of the displaced portion of said one of the pieces is from the direction of the outer surface of the same.

7. The method of claim 5 wherein the direction of penetrationof the displaced portion of said one of the pieces is from the direction of the outer surface of said other of the pieces.

8. The method of uniting overlying pieces of material which comprises forming a pair of substantially parallel spaced incisions through both of the pieces, forming a pair of recesses one outside of each incision and communicating therewith, bending the material between the incisions outwardly until the displaced portion of one of the pieces lies only a minimum clearance distance beyond the outer surfaces of the recessed portions of the other of the pieces, and spreading the displaced portion laterally into said recesses without substantial thinning of its outer margins by cleaving it centrally, the direction of cleavage being substantially parallel to that of the incisions, thereby causing it to underlie and engage the other of the pieces, to lock the pieces together through an integral fastener of substantial strength and minimum projection beyond the surface of the material.

9. A fastener for uniting overlying pieces of material which comprises integral portions of the pieces defined by a pair of substantially parallel spaced incisions through the pieces and displaced so that the incised portion of one of the pieces lies beyond the outer surface of. the other of the pieces, the displaced portion of said one of the pieces being formed in two sections spread apart laterally from each other and retaining substantially their original thickness at their outer margins, the outer margins of said sections underlying and engaging the outer surface of said other of the pieces, thereby locking the pieces tightly together.

10. A fastener for uniting overlying pieces of material which comprises integral portions 'of the pieces defined by a pair of substantially parallel spaced incisions through the pieces, said portions being displaced so that the incised portion of one of the pieces lies beyond the outer surface of the other of the pieces, said other of the pieces having spaced recesses in its said outer surface, the displaced portion of said one of the pieces being formed in two sections separated laterally and retaining substantially their original thickness, said sections being received at least in part in said recesses and underlying and engaging said other of the pieces thereby locking the pieces tightly together.

IVAN A. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name 7 Date 56,494 Gordon July 1'7, 1866 512,021 Gould Jan. 2, 1894 977,178 Ferguson Nov. 29, 1910 2,254,558 Williams Sept. 2, 1941 2,288,308 Williams June 30, 1942 

